1. Technical Field
The invention relates to a hologram recording material suitable for recording large capacity information by making use of hologram recording, a hologram recording medium using the same and a hologram recording method using the hologram recording medium.
2. Related Art
In the holographic data storage, polarization can be recorded when, as a material for recording a hologram, a photochromic material such as a polymer material having, in a molecule thereof, an azobenzene skeleton whose orientation changes in trans-cis under irradiation of light (hereinafter occasionally referred to as “azo-polymer”) is selected.
The polarization recording is a useful recording method characteristic to the hologram recording in which data can be locked for security and used to calculate. However, azopolymers or the like that is under study at present as a recording material for hologram recording media that can record the polarization, being reversible in a photoisomerization reaction thereof, cannot permanently keep the polarization recording; accordingly, it is under study as a rewritable material.
In the holographic data storage, there are a large need for write-once type hologram recording media where information once recorded is not lost, rather than rewritable hologram recording media because of its large capacity of recording.
As one that satisfies such needs, there is known a hologram recording medium that uses a photopolymerizable polymer recording material (so-called photopolymer) that can record information by making use of an irreversible reaction such as a polymerization reaction occurring upon light irradiation. However, in this type of the medium, the foregoing advantages cannot be obtained since the polarization recording cannot be carried out. Furthermore, when multiplex recording is applied, there is a disadvantage that the sensitivity significantly decreases as the recording is repeated.